1. Statement of the Technical Field
The present invention relates to manufacturing test processes and more particularly to a method of improving the effectiveness of manufacturing test coverage.
2. Description of the Related Art
Generally, in a manufacturing system test environment, a factory assembles parts from suppliers into products, tests these products for full functionality and potential early failures, and finally ships functioning products to customers based on custom-order. If a customer experiences failure issues with a product, it is either repaired in the field or sent back to factory for repair. The field failure information is gathered on a regular basis for analysis for improving the engineering, manufacturing, and test processes. This, of course, is mostly a manual process.
Manufacturing test cases are generally designed based on inputs from system designers or engineering personnel to uncover issues during the manufacturing system integration phase. Reliability and availability issues including fault and performance degradation are often reported after a system has been installed and used. Usually, the most important and critical test cases are based on problems found in the field during product installation and up to three months after installation.
Typically, field failure data is manually analyzed then used to manually review manufacturing test cases. The field issues are gathered, then analyzed and managed by people and fed back manually to groups like Product Development and Manufacturing and Testing. Often, new test cases are manually added to the manufacturing test suite instead of optimizing existing test cases. Thus, the test case development process remains inefficient causing a slow process since it relies on manual optimization of new test cases to be added to the manufacturing test suite instead of optimizing existing test cases.
The ability of the manufacturing test process to ensure customer satisfaction can be measured based on test coverage. In order to properly target the test process it is important to understand the fault spectrum of interest, the likelihood of a defect or functional failure, and the impact of the failure on the customer. Issues with current manufacturing test coverage include the assumption that all failures are equally likely. Another issue is the impact of the failure eventually reaching the field. Current methods fail to incorporate the notion that not all defects or failures will have the same impact to the customer and not all test cases need to be run for a specific order configuration. For instance, not testing for a safety related defect would be more serious than a cosmetic issue.
Current methods do not offer automatic integrated field feedback to effectively optimize manufacturing test cases based on reported field failure data. Additionally, with current methods, there is a lack of re-using or enhancing existing manufacturing test cases. However, adding new test rules to the manufacturing test suite can continuously increase the size of the manufacturing test bucket and the manufacturing test cycle time.